Bring a medium pot of water to a boil. Stir in 1 cup of brown rice. Cook, without stirring, for 15 minutes. Drain well.
While rice boils:
Dice onion. Clean and dice mushrooms.
Roll lemon on the counter, using the palm of your hand, several times to help with juicing. Zest lemon. Cut lemon in half and juice overtop of a mesh strainer (to catch the seeds). Set aside.
Add 2 tablespoons oil to a large deep skillet. Heat over medium heat. Add onion and cook until onion softens.
Add the drained rice to the onion. Cook, stirring occasionally, until it is glossy and coated with oil (just a few minutes).
Add ½ teaspoon salt, ¼ teaspoon pepper, ¼ cup water and ¼ cup white wine vinegar. Stir and let the liquid bubble away.
Begin to add the vegetable stock about ½ cup at a time. Stir after each addition and every minute or so. When the stock is just about absorbed, add more. The mixture should not be soupy or dry. Keep the heat medium to medium-high and stir frequently.
After about 15 minutes of adding the vegetable stock, stir in the mushrooms and cook until they release their liquid and the mixture again becomes dry.
Stir in lemon zest, lemon juice, parmesan cheese and parsley.
Serving Size 3/4 cup
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.